Drive signal storage and direct drive in display systems

ABSTRACT

Apparatus addressing multi-position display devices directly from semiconductor integrated circuits and passive driving of the display electrodes also from such circuits. The apparatus determines the magnitude of the bias voltage and of the selection signals that are applied to operate threshold-responsive devices, including gas discharge display tubes and panels, independent of the input data signals. Energy for a segmented display is accumulated in a plurality of capacitance elements, responsive to input data pulses of a first polarity, and the opposite potential from them then activates the device. This develops the necessary potential of proper polarity for operating the display, without need of active inverters for the input signals. In one system the storage capacitors are automatically charged to a potential from which selection pulses of predetermined duration can further charge them sufficiently to ionize a display position. The cathode bias which proved to be suitable for a particular display device is stored between display periods and signal blanking is introduced between display periods on the data lines which connect to the display electrodes. The apparatus also improves the uniformity of brightness of different display patterns and enables the control of display brightness by variation of the rate at which the apparatus is pulsed.

United States Patent [191 Holz June 28, 1974 DRIVE SIGNAL STORAGE AND DIRECT DRIVE IN DISPLAY SYSTEMS [75] Inventor: George E. Holz, North Plainfield,

[73] Assignee: Burroughs Corporation, Detroit,

Mich.

22 Filed: July 13, 1972 21 Appl. No.: 271,591

[52] US. Cl.....; 315/169 R, 315/173 [51] Int. Cl. 1105b 37/02 [58] Field of Search 315/169 R, 169 TV, 173; 313/ 109.5

[56] References Cited UNITED STATES PATENTS 2,810,861 10/1957 Jackson et al. 315/169 R 3,409,800 11/1968 Myers et al 315/169 TV 3,435,138 3/1969 Borkan 315/169 R 3,679,933 7/1972 Nakada et al. 315/169 TV Primary Examiner-Herman Karl Saalbach Assistant Examiner-Richard A. Rosenberger Attorney, Agent, or Firm--Robert A. Green; Edward G. Fiorito; Paul W. Fish [5 7 ABSTRACT Apparatus addressing multi-position display devices directly from semiconductor integrated circuitsand passive driving of the display electrodes also from such circuits. The apparatus determines the magnitude of the bias voltage and of the selection signals that are applied to operate threshold-responsive devices, including gas discharge display tubes and panels, independent of the input data signals. Energy for 21 segmented display is accumulated in a plurality of capacitance elements, responsive to input data pulses of a first polarity, and the opposite potential from them then activates the device. This develops the necessary potential of proper polarity for operating the display, without need of active inverters for the input signals.

in one system the storage capacitors are automatically charged to a potential from which selection pulses of predetermined duration can further charge them sufficiently to ionize a display position. The cathode bias which proved to be suitable for a particular display device is stored between display periods and signal blanking is introduced between display periods on the data lines which connect to the display electrodes. The apparatus also improves the uniformity of brightness of different display patterns and enables the control of display brightness by variation of the rate at which the apparatus is pulsed.

12 Claims, 3 Drawing Figures PATENTED JUN 2 8 I974 SHEET 2 0f 3 U6 Tx Omrmmvmwhw +X...-mm. u oom 00m mom 9m PMENTEDJUN 28 I974 SHEET 3 BF 3 MOM DOM UOM @Qm omrwmvmwhw OON DRIVE SIGNAL STORAGE AND DIRECT DRIVE IN DISPLAY SYSTEMS BACKGROUND OF THE INVENTION This invention relates to apparatus for operating segmented-electrode display devices which are thresholdresponsive to selection signals applied to them, including gas discharge display tubes and display panels. More particularly, the invention relates to apparatus for addressing multiple-position gas discharge devices directly from semiconductor integrated circuits and the like and to passive driving or operation of the display elements thereof from the same circuits.

Various segmented-electrode display devices have been developed recently for use as readout indicators for electronic calculators and the like. One such device is the PANAPLEX panel display which is a multipleposition gas discharge device having a plurality of segmented display cathodes and a plurality of associated anodes. Such display panels usually include several groups of cathode segments, with corresponding segments of the different groups being interconnected, and an anode electrode associated with each group of cathodes.

In a recently developed version of the PANAPLEX panel display, the cathode elements are deposited or formed along the front surface of an insulating base plate and planar anode electrodes are spaced closely above the cathodes. It has been discovered that either the anodes or the cathodes thereof, if they are sufficiently biased toward discharge, can be operated by voltage signals which approximate the maximum voltage excursions that are allowable on the outputs of some metal-oxide semiconductor (MOS) integrated circuits.

Such MOS integrated circuits are available in the form of calculator circuits, decoder circuits, counters, registers, and the like. Substantial economies would re sult if the display positions of such devices could be both addressed and operated directly, or at least passively, from these circuits with a minimum amount of additional circuitry.

Some of these integrated circuits provide output signals for display elements or segments which are of the wrong polarity for driving the cathodes of gas discharge devices. Also, some of these MOS signal circuits or sources do not provide inactive intervals between successive sets of data signals, which would protect against spurious glow in the display device, known as signal blanking. Furthermore, the biasing requirements for such devices change with temperature and mode of operation and must be compensated for. Each of these circumstances usually require that active drivers or buffers be connected between the MOS or other low voltage signal source and at least one set of the electrodes of the display device.

A further difficulty with some display control apparatus is that the brightness of the display could only be decreased conveniently by reducing the drive current to the electrodes. This often results in partial glow discharges. Furthermore, some circuits tend to drive the elements of segmented-electrode displays at different levels depending on how many of the segments are selected. A single segment display is slow to ionize a display position and oneor two-segment patterns thus require increased ionizing potentials if different display patterns are to be relatively uniform in brightness.

SUMMARY OF THE INVENTION Accordingly, an object of this invention is to operate the display elements of multiple-position gas discharge devices from passive circuit elements coupled to semiconductor integrated circuits or the like.

Another object is to accumulate energy for driving the display electrodes of segmented-character display devices in response to input data signals of the wrong polarity, without active signal inverters for them.

A further object of the invention is to control the brightness of segmented-electrode display devices and to improve the uniformity of display brightness in such devices.

The invention provides drive apparatus for segmented-character display devices which includes capacitance elements passively coupled to the display segments and means for selectively charging the capacitance elements to a sufficient potential, responsive to a set of input data signals, to activate the display device or position in'cooperation with bias potentials and digit address signals applied to it.

In one embodiment, the apparatus charges the capacitance elements in response to the input data signals and builds-up bias potential for the display electrodes until the display is activated. The accumulated bias voltage is stored by the apparatus and is automatically adjusted as the threshold potential of the device changes. In another embodiment, the capacitance elements are charged to an initial potential during a blanking interval between digit display periods and then are raised to a higher potential responsive to the input data signals.

DESCRIPTION OF THE DRAWINGS Other advantages and features of the invention are made clear in the following description, relating to the attached drawings, wherein:

FIG. 1 is an enlarged, exploded view of a segmentedelectrode display panel shown in perspective;

FIG. 2 is an electrical schematic diagram of one operating system embodiment for such a panel; and

FIG. 3 is an electrical schematic diagram of another operating system embodiment for such a panel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The display panels described herein are thin, flat, sheet-like members which may have substantially any desired shape and size, and may include substantially any number of character display positions. The panels may include any suitable ionizable gas such as neon, argon, xenon, etc., singly or in combination, with a vapor of a metal such as mercury usually included in the gas to minimize cathode sputtering. A wide range of gas pressures may be used, for example, from about 20 to about 250 Torr at ambient temperature with about to Torr being a commonly used pressure range.

Referring to FIGS. 1-3, a display device 10 embodying the invention includes an insulating base plate 20 of glass, ceramic, or the like, with an inexpensive glass being suitable and preferred. A plurality of conductive connectors or runs 30A to 306 are formed on the top surface of the insulating plate 20. The runs 30 are parallel to each other and are aligned with the horizontal axis of the base plate. Seven such runs 30A to 300 are shown; however, more or fewer may be provided, the

number being determined by the total number and type of characters to be displayed. The runs 30 may be formed by an evaporation process, a silk-screen process, an electroless plating process or the like, or they may be discrete strips of metal, heat-sealed, and plasma-sprayed, or otherwise secured to the insulating plate 20. A silk-screen printing process is particularly suitable because it is fast, efficient, and reproducible.

A second thin layer 40 of insulating material such as glass or ceramic is formed on the conductive runs 30, preferably by a silk-screen process, and the second layer 40 includes a plurality of groups of vias or apertures 50A to 500, each aperture exposing one of the runs 30A to 306. Thus, each group of apertures includes aperture 50A which exposes run 30A, aperture 503 which exposes run 308, aperture 50C which exposes run 30C, etc. Four such groups of apertures are illustrated.

Panel includes a group of cathode electrodes 60 (A to G) for each group of apertures 50. The cathodes are generally elongated bars or segments, and they are usually arrayed in a figure eight pattern, as is well known in the art. The cathodes 60 may be formed on insulating layer 40 by means of a silk-screen process using a conductive paste such as palladium-gold, platinum-gold, palladium-silver, or the like. Each cathode element is in contact with one of the runs exposed by one of the apertures or vias 50, and it substantially fills the aperture 50 and covers a portion of layer to achieve the desired shape and size.

The cathodes 60A, 60B, etc. may also be formed of discrete strips of metal, preferably brazed to a conductive run 30 by means of a mass of brazing material deposited in each of the apertures in the insulating layer 40. The brazing material itself may be deposited by a silk-screen process. One suitable brazing material is a gold-germanium substance known as FORMON and sold by E. l. DuPont de Nemours & Co. The cathodes may also be formed in any other suitable manner such as by electrolytic or electroless plating of nickel or the like or by are plasma spraying through a suitable mask.

Thus, cathodes are preferably thin, flat members which do not project to any significant extent above the prise thin, transparent conductive films of gold, NESA,

or the like formed on the lower surface 95 of the panel face plate or viewing plate 100 which is made of glass. The anode films are of the order of a few Angstroms thick and, in effect, are coplanar with the bottom surface 95 of the face plate. Thus, the anodes, for all practical purposes, do not project into the gas discharge space in the panel. The anode films are generally rectangular in shape, or are otherwise shaped, depending on the orientation of the cathodes. Anodes 90 are dimensioned and positioned so that they overlay the total area defined by the associated group of cathode electrodes. If desired, each anode 90 may be somewhat narrower and shorter than the area defined by its cathodes as shown, but in any case, the anode must overlay and be in operative relation with a sufficient portion of each of its cathodes. Other suitable anode shapes may be employed, depending upon the character and symbol configuration of the cathodes to be operated.

Preferably, the spacing between each anode and its group of cathodes 60 should be of the order of 20 to 25 mils, and the spacing between each anode and the adjacent group of cathodes should be of the order of 30 to 40 mils. With this relationship at the usual pressure range, each anode is in a favorable operating position with respect to its own cathodes, but is sufficiently remote from adjacent groups of cathodes so that the panel may be operated over a suitably wide range of potentials without developing cross-talk between adjacent groups of electrodes. Another factor tending to prevent cross-talk is the location of the anodes in substantially coplanar relation with the surface of the glass cover plate and not projecting into the gas space in which cathode glow takes place.

Another advantage of the close spacing of each anode to its group of cathodes, thus providing a thin volume of gas, is that metastable-state atoms produced in the gas during discharge diffuse to, and are readily neutralized at, these closely spaced surfaces. In addition, excited or charged particles are readily swept out through the anode-cathode circuit path. The tendency for cross-talk to develop is minimized by these two factors.

The top glass cover plate is of substantially the same length as the insulating layer 40 and the bottom plate 20, and it is spaced from the base plate 20 by a rectangular glass frame which is disposed between the top glass plate 100 and the insulating layer 40. Frame 110 may be an integral part of the top and/or bottom plates. The rectangular frame serves thus to provide the desired spacing between each anode and its associated group of cathode electrodes. The top glass plate 100 is also preferably slightly wider than the insulating layer 40 and base plate 20 so that one edge, say the upper edge, extends beyond the remainder of the panel and is accessible to permit the connection of leads 140 to each of the anode films 90. The three glass members 20, 100, and 110 are sealed together in any suitable manner, for example, by means of a seal formed of a glass frit or the like.

Connection to the runs 30 corresponding be made, as an example, by means of L-shaped pins or contacts 144 which are embedded in the seal 120 at one or both ends of the panel.

The panel 10 can be filled with the desired gas atmosphere through a tubulation not shown secured to the base plate 20 and communicating with the interior of the panel through a hole not shown in plate 20 and layer 40, and, generally, mercury is introduced from a glass capsule (not shown) held in the tubulation and suitably processed at the desired stage in the assembly process.

The invention relates to panel-type segment display devices which include a plurality of groups of cathode electrodes which comprise elongated bars or segments arrayed in a pattern so that the cathodes of each group can be selectively energized to display a character. For reasons of economy, corresponding electrodes in each group, usually cathodes, have a common conductor. The anodes are separately energizable and the panel is operated in a multiplex mode of operation. In this mode of operation, operating potential is applied to selected cathode conductors at time t and thus to selected cathode segments, and the first a'node is energized and a first character is displayed by the energized cathode segments in the first group. At time t,,, operating potential is applied to the same or other cathode conductors and to the second anode and a second character is displayed by the second group of cathodes. This same operation is carried out for each character position, and it is repeated continually along the entire dis play panel at a suitable frequency so that stationary but changeable characters can be displayed.

The system of FIG. 2 illustrates an apparatus for op erating a display device having nine groups of eight cathode segments each connected by cathode conductors 30 (A-H). An anode electrode 90 is associated with each group of cathodes. The anodes are driven directly over conductors 92 from a data signal source 300 such as an MOS calculator chip, for example. The cathodes are driven from data source 300 through conductors 320 and passive circuits including capacitors 275. The digit outputs of the data source on conductors 92 are also connected to leads 94 of keyboard 200 by conductors 98 and 215. The outputs of keyboard 200 are connected through isolating diodes 205 to control input lines 210 of the data source 300. Data source 300 is sequenced by a clock signal applied to terminal 310, and is biased by positive voltage terminal 190, negative voltage terminal 180, and by ground.

Each digit output lead 92 is connected directly to a corresponding anode 90 and by a conductor 98 to a diode 96 whose cathode is connected to the common anode pull-down resistor 225, which holds the anodes below operating potential normally. Data source 300 energizes anodes 90 in sequence and strobes keyboard 200 at the same time. Keyboard output signals on lines 210 are sensed by the data source and cathode logic signals are generated on output lines 320 for display at the proper digit position in the device.

At the beginning of each digit strobe signal on a conductor 92, the positive voltage step at resistor 22S couples through capacitor 230 and resistors 232 and 234 to provide base drive for transistor 240. The output at the collector of transistor 240 which is coupled to positive terminal 190 by current-limiting resistor 242, is fed through capacitor 246 and resistor 248, amplified by transistor 250, and applied to bus 260 which is connected to the individual cathode capacitors 275 by diodes 265. Transistor 240 thus provides a negative pulse to bus 260 at the beginning of each new digit period which combines with the segment logic outputs of data source 300 to drive capacitors 275, which then discharge through display device 10 when it fires.

When a segment output 320 is not activated, it remains in a high impedance or open state and both sides of the corresponding capacitor 275 swing minus and plus and no charging of the capacitor takes place. Also, since the cathode strobe pulses from transistor 240 are present on the cathodes for a shorter time than the normal ionization delay of the device at the voltages utilized, no discharge takes place and the segment remains off.

When a segment output 320 from data source 300 is closed or activated, however, it holds one side of the corresponding cathode capacitor 275 to a positive voltage and the negative pulse through diodes 265 charges the corresponding capacitors 275 negatively. This charge remains on the selected cathode capacitors 275 until display device 10 ionizes and discharges the capacitors positive to the minimum sustaining voltage of the device. Resistors 270 continue to discharge capacitors 275 during the remainder of the digit time to provide additional off-bias for the de-energized display positions.

In a multiplexed display it is desirable to provide a blanking interval each time a new digit position is to be energized to prevent spurious glow of previously energized cathodes in the new position. It increases the effective isolation between successive display positions in a multiple-position device. This is because the blanking interval insures a decay below the sustaining ionization potential at the electrodes of a de-energiz'ed position before a subsequent'digit position is energized. In the system of FIG. 2 blanking on the cathodes is provided automatically when capacitors 275 are dischargedthrough the device and also through resistors 270. The anodes are ordinarily blanked by data source 300 and no other blanking in this system since the cathodes are held below the sustaining ionization potential during each cycle once capacitors 275 become discharged.

Transistor 250 is the basis of a bias regulator circuit which automatically seeks the proper operating bias point for display device 10. When transistor 250 is lightly loaded through'its emitter resistor 252 by only a few cathodes, it operates as a high current gain emitter-follower amplifier. Capacitor 246 serves to integrate the pulse current into capacitors 275 by discharging the capacitors through resistors 270 and thereby to hold the operating bias provided by transistor 250 over a complete display cycle. If segments are addressed, pulses from the collector of transistor 240 cause charging of the appropriate cathode capacitors 275, largely with current drawn from the negative voltage supply terminal through the collector of transistor 250. If the display panel 10 does not fire during a cycle due to insufficiently negative bias of capacitor 246, however, the negative voltage from the cathode capacitors 275 relative to that on capacitor 246 will cause a current through resistors 248, 254 and 270 which increases the negative bias on capacitor 246 with each display cycle until the device fires.

After the panel has begun to discharge at the addressed segments, the bias voltage on capacitor 246 reaches an equilibrium condition determined by the effective gain of transistor 250, the off-bias appearing on cathode capacitors275 after discharge, and the charging current through resistors 270 after cathode strobing but during ionization delay in the device. By appropriate choice of resistor 254 and emitter resistor 252 which operate in conjunction with diodes 258 to control the gain of transistor 250 during pulse amplification, the proper bias point can be obtained. When transistor 250 is heavily loaded by many or all of the cathodes, diodes 258 conduct and decrease the current gain of transistor 250 toward unity to reduce the amount of charge that will be stored in capacitors 275, since less is needed in that case to ionize the display. Conversely, resistor 280 connected between bus 260 and ground introduces a positive bias which compensates for the tendency of the bias point to become too far negative when only one or a few segments are activated.

The amount of cathode segment drive in this system is charge-limited by series capacitors 275 connected to them rather than being current-limited with series resistors. The brightness of the display, therefore, is a function of the clock rate, a fixed input charge or energy being stored during each refresh cycle, and also of the value of capacitors 275. The brightness of the display is only slightly affected by variations in the negative voltage supply on terminal 150 or by variations in the re-ionization delay.

In the system of FIG. 3, the digit outputs 92 of data source 300 are again connected directly to anodes 90 and to leads 94 of keyboard 200 by conductors 98 and isolation diodes 104. The anodes are coupled through resistors 106 to a common pull-down resistor 325 which is connected at the other end to voltage terminal 330. Cathode blanking is synthesized by transistors 335 and 355 from anode blanking provided by data source 300 from the common anode return to resistor 325. A negative-going signal on the base of transistor 335 is amplified and couples a negative signal through capacitor 345 to switch on transistor 355 for blanking the cathode drivers through diodes 365. Also, resistor 420 in the cathode power supply return at terminal 425 protects the drivers from damage during turn-on and limits cathode current to prevent other transient arcing conditions on the tube which are otherwise possible when voltages are applied between the electrodes of gas discharge devices.

A PNP transistor driver 375 is provided for each of the cathodes and will invert signals applied to its base by'segment logic signals on conductors 310 from data source 300. Series cathode capacitors 405 are initially charged to over half of the ionization voltage .by current through transistor 355, diodes 395, diodes 410, and common cathode return 400 to resistor 420. This path is interrupted when transistor 355 is turned off to end blanking and capacitors 405 will be charged through resistors 390 toward approximately twice the initial level of potential if a positive logic signal is received by transistor 375 from the associated segment signal conductor 310 to hold it off. This will approximately double the potential in the selected cathodes and will cause ionization in display device 10. If, instead, no segment signal is received by transistor 375, it will conduct and prevent the additional charging of capacitor 405 and hence prevent ionization and discharge in the device.

Resistors 390 provide current-limitation for the conduction of current from the cathodes to capacitors 405 in the system and pulls the cathodes toward the required ionization voltage through capacitors 405 during ionization delay. When transistor 375 is turned on, it restores the capacitor 405 and holds the coresponding cathode in the off condition.

Although the preferred embodiments of the invention have been described in detail, it should be understood that the present disclosure has been made by way of example only. Many modifications and variations of the invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically disclosed.

What I claim is:

l. Multiple-position display device and system for operating the device, said device having a plurality of groups of cathode elements and an anode associated with each group, corresponding cathodes of the differ ent groups being interconnected by a single common conductor, there thus being a single common conductor for each cathode element in each of said groups, said system comprising first means for applying positive-going signal voltages coupled to each of the anodes individually and sequentially, anodes not so addressed being held off 8 by a potential lower than said positive-going signal voltages,

a capacitor having one side coupled to each of the single common conductors and thus to one cathode element in each group to provide drive currents directly to them at a potential suitable to activate selected cathode elements at a display position having an addressed anode, the other side of each said capacitor being coupled to a data line at the output of a source of data signals, and

second means coupled to each said capacitor for charging each said capacitor proportionally to the number of data lines which carry data signals and in a direction to cause the associated cathode element to exhibit cathode glow.

2. The system defined in claim 1 wherein said second means includes an active element providing a current flow path coupled to said capacitor, and

another capacitor coupled to the input of said active element, said other capacitor being coupled to all of said common conductors whereby the charge thereon is proportional to the number of data lines which carry data signals.

3. The system defined in claim 1 wherein said first means includes a separate signal output line coupled to each of said anode electrodes and through a diode to a bus which is connected to a resistor for applying holdoff bias potential to all of said anode electrodes which do not receive a positive-going signal voltage,

said bus also being coupled through an active element which is coupled to said first capacitor.

4. The system defined in claim 1 wherein said first means includes a separate signal output line coupled to each of said anode electrodes and through a diode to a first bus which is connected to a resistor for applying holdoff bias potential to all of said anode electrodes which do not receive a positive-going signal voltage,

said first bus also being coupled to a first semiconductor device having an output electrode coupled to a first path including a second capacitor and a resistor in series,

a second bus coupled through a resistor to each of said common conductors,

a second semiconductor device coupled to said second bus to provide current thereto,

the output of said first semiconductor device being coupled through said first path to the input of said second semiconductor device and to said second bus through a second pathincluding diode means and resistive means in parallel.

5. Multiple-position display device and system for operating the device wherein said device has a plurality of groups of cathode elements and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single conductor for each cathode element in each of said groups, said apparatus comprising a source of data signals,

first means for applying positive-going signal voltages coupled to each of the anodes individually and sequentially, anodes not so addressed being held off by a potential lower than said positive-going signal voltages,

a capacitor having one side coupled to each of the single common conductors and thus to one cathode element in each group to provide drive currents directly to them at a potential suitable to activate selected cathode elements at a display position having an addressed anode, the other side of each said capacitor being coupled to a data line at the output of said source of data signals, second means coupled to each said capacitor for charging each said capacitor to a first level below cathode ionization potential at which a cathode exhibits cathode glow, and third means coupled between said source of data signals and each of said capacitors for charging each said first capacitor to a second level equal to or greater than cathode ionization potential when a data signal is present at said third means, said first means including a separate lead connected from said data source to each said anode and through a resistive path to first and second semiconductor devices in series, a bus coupled through separate diodes to each of said capacitors, the output of said first and second semiconductor devices being connected to said bus for applying holdoff potentials thereto and to said capacitors when said first and second semiconductor devices are in a conductive state, said capacitors being charged to said first level when said first and second devices are in said conductive state, said first and second semiconductor devices being turned off and said third means being selectively energized when information signals are present. 6. Multiple-position display device and system for operating the device wherein said device has a plurality of groups of cathode elements and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common conductor for each' cathode element in each of said groups, said apparatus comprising a source of data signals, I first means for applying positive-going signal voltages coupled to each of the anodes individually and sequentially, anodes not so addressed being held off by a potential lower than said positive-going signal voltages,

a capacitor having one side coupled to each of the single commmon conductors and thus to one cathode element in each group to provide drive currents directly to them at a potential suitable to activate selected cathode elements at a display position having an addressed anode, the other side of each said capacitor being coupled to a data line at the output of said source of data signals,

second means coupled to each said capacitor for charging each said capacitor to a first level below cathode ionization potential at which a cathode exhibits cathode glow, and

third means coupled between said source of data sig nals and each of said capacitors for charging each said first capacitor to a second level equal to or greater than cathode ionization potential when a data signal is present at said third means,

said first means including a separate lead connected from said data source to each said anode and through a resistive path to first and second semiconductor devices in series,

a bus coupled through separate diodes to each of said capacitors,

the output of said first and second semiconductor devices being connected to said bus and to a current flow path which includes a first diode, said capacitor, a second diode, a resistor and a source of bias potential whereby each of said capacitors is charged to a relatively low level and holdoff potential is applied to each of said common conductors and said cathode elements do not exhibit cathode glow,

said third means including separate semiconductor 7. Multiple-position display device and system for operating the device, said device comprising a gas-filled envelope including a plurality of groups of cathode electrodes and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common cathode conductor for each cathode electrode in each of said groups, said system comprising a firstbus connected to all of said common conductors,

a semiconductor logic circuit including: a plurality of output leads, each coupled through a capacitor to one of said common cathode conductors for applying data signals thereto, an anode lead coupled to each of said anodes, a plurality of input leads, and means by which a clock signal can be applied to the logic circuit to sequence the logic circuit, and

a keyboard having: a plurality of keys, each representing a unit of information; a plurality of output leads, one from each key and connected to one of said input leads to said logic circuit; and a plurality of strobe leads, each connected to one of said anode leads of said logic circuit and thus to one of said anodes,

each of said anode leads and the keyboard strobe lead to which it is connected being coupled through a pulse-generating circuit to said bus which is connected to said common cathode conductors, whereby at a character position when the anode is energized and driven in a positive direction, all of said common cathode conductors and one side of said capacitor are driven in a negative direction,"

the presence of a cathode data signal on any one of said output leads from said logic circuit appearing at the other side of the associated one of said capacitors and driving the associated common cathode conductor sufficiently negative to cause the cathode associated with the energized anode to exhibit cathode glow,

the absence of a cathode data signal on any one of said output leads from said logic circuit preventing any of said capacitors from charging to a potential sufficient to cause the associated cathode to exhibit cathode glow.

8. The system defined in claim 7 and including a second bus,

said pulse generating circuit including a first semiconductor device having input and output electrodes and a current flow path therethrough, and a second semiconductor device having input and output electrodes and a current fiow path therethrough,

all of said anodes being connected to said second bus,

said second bus itself being coupled (1) through an anode pull-down resistor to a negative power supply, and (2) to the input of said first semiconductor device of said pulse-generating circuit,

the output of said first semiconductor device of said pulse-generating circuit being coupled through another capacitor and a resistive path (1) to the input of said second semiconductor device, (2) to the current flow path through said second semiconductor device, and (3) to said first bus, said first bus thus being connected to said current flow path through said second semiconductor device and to all of said common cathode conductors.

9. Multiple-position display device and system for op erating the device, said device comprising a gas-filled envelope including a plurality of groups of cathode electrodes and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common cathode conductor for each cathode electrode in each of said groups, said system comprising a first bus connected through individual coupling capacitors to each said common conductor,

a semiconductor logic circuit including: a plurality of output leads, each coupled through a separate pulse-generating semiconductor device and one of said coupling capacitors to one of said common cathode conductors for applying data signals 7 thereto, an anode lead coupled to each of said anodes, a plurality of input leads, and means by which a clock signal can be applied to the logic circuit to sequence the logic circuit,

senting a unit of information, a plurality of output leads, one from each key and connected to one of said input leads to said logic circuit; and a plurality of strobe leads, each connected to one of said anode leads of said logic circuit and thus to one of said anodes,

each of said anode leads and the keyboard strobe lead to which it is connected being coupled through said common pulse-generating circuit to said bus and thus through each said coupling capacitor to one of said common cathode conductors, whereby at a character position when the anode is energized and driven in a positive direction, if the associated pulse-generating semiconductor device receives a data signal from said logic circuit, then the associated cathode exhibits cathode glow.

10. The system defined in claim 9 and including a second bus, a third bus, a fourth bus, and a fifth bus,

said second bus being coupled through an anode pulldown resistor to a negative power source and to the input of said pulse-generating circuit, the output of said pulse-generating circuit being coupled to said first bus, said first bus being coupled through a diode to the side of each of said capacitors remote from the associated common cathode conductor,

each said separate pulse-generating semiconductor device being coupled to said side of its said capacitor through its output electrode,

each of said data lines being coupled to the input of one of said pulse-generating semiconductor devices.

11. The system defined in claim 10 wherein said pulse-generating circuit comprises first and second PNP transistors connected in series, and each said pulse-generating semiconductor device comprises a third PNP transistor.

12. The system defined in claim 10 wherein said pulse-generating circuit comprises first and second PNP transistors connected in series, and each said pulse-generating semiconductor device comprises a third PNP transistor,

said second bus being connected to the base of said first PNP transistor, said third bus being connected through a resistive path to the base of each of said third PNP transistors, said fourth bus being connected to the emitter of each of said third transistors, and said first bus being connected to the collector of said second PNP transistor. 

1. Multiple-position display device and system for operating the device, said device having a plurality of groups of cathode elements and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common conductor for each cathode element in each of said groups, said system comprising first means for applying positive-going signal voltages coupled to each of the anodes individually and sequentially, anodes not so addressed being held off by a potential lower than said positive-going signal voltages, a capacitor having one side coupled to each of the single common conductors and thus to one cathode element in each group to provide drive currents directly to them at a potential suitable to activate selected cathode elements at a display position having an addressed anode, the other side of each said capacitor being coupled to a data line at the output of a source of data signals, and second means coupled to each said capacitor for charging each said capacitor proportionally to the number of data lines which carry data signals and in a direction to cause the associated cathode element to exhibit cathode glow.
 2. The system defined in claim 1 wherein said second means includes an active element providing a current flow path coupled to said capacitor, and another capacitor coupled to the input of said active element, said other capacitor being coupled to all of said common conductors whereby the charge thereon is proportional to the number of data lines which carry data signals.
 3. The system defined in claim 1 wherein said first means includes a separate signal output line coupled to each of said anode electrodes and through a diode to a bus which is connected to a resistor for applying holdoff bias potential to all of said anode electrodes which do not receive a positive-going signal voltage, said bus also being coupled through an active element which is coupled to said first capacitor.
 4. The system defined in claim 1 wherein said first means includes a separate signal output line coupled to each of said anode electrodes and through a diode to a first bus which is connected to a resistor for applying holdoff bias potential to all of said anode electrodes which do not receive a positive-going signal voltage, said first bus also being coupled to a first semiconductor device having an output electrode coupled to a first path including a second capacitor and a resistor in series, a second bus coupled Through a resistor to each of said common conductors, a second semiconductor device coupled to said second bus to provide current thereto, the output of said first semiconductor device being coupled through said first path to the input of said second semiconductor device and to said second bus through a second path including diode means and resistive means in parallel.
 5. Multiple-position display device and system for operating the device wherein said device has a plurality of groups of cathode elements and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single conductor for each cathode element in each of said groups, said apparatus comprising a source of data signals, first means for applying positive-going signal voltages coupled to each of the anodes individually and sequentially, anodes not so addressed being held off by a potential lower than said positive-going signal voltages, a capacitor having one side coupled to each of the single common conductors and thus to one cathode element in each group to provide drive currents directly to them at a potential suitable to activate selected cathode elements at a display position having an addressed anode, the other side of each said capacitor being coupled to a data line at the output of said source of data signals, second means coupled to each said capacitor for charging each said capacitor to a first level below cathode ionization potential at which a cathode exhibits cathode glow, and third means coupled between said source of data signals and each of said capacitors for charging each said first capacitor to a second level equal to or greater than cathode ionization potential when a data signal is present at said third means, said first means including a separate lead connected from said data source to each said anode and through a resistive path to first and second semiconductor devices in series, a bus coupled through separate diodes to each of said capacitors, the output of said first and second semiconductor devices being connected to said bus for applying holdoff potentials thereto and to said capacitors when said first and second semiconductor devices are in a conductive state, said capacitors being charged to said first level when said first and second devices are in said conductive state, said first and second semiconductor devices being turned off and said third means being selectively energized when information signals are present.
 6. Multiple-position display device and system for operating the device wherein said device has a plurality of groups of cathode elements and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common conductor for each cathode element in each of said groups, said apparatus comprising a source of data signals, first means for applying positive-going signal voltages coupled to each of the anodes individually and sequentially, anodes not so addressed being held off by a potential lower than said positive-going signal voltages, a capacitor having one side coupled to each of the single commmon conductors and thus to one cathode element in each group to provide drive currents directly to them at a potential suitable to activate selected cathode elements at a display position having an addressed anode, the other side of each said capacitor being coupled to a data line at the output of said source of data signals, second means coupled to each said capacitor for charging each said capacitor to a first level below cathode ionization potential at which a cathode exhibits cathode glow, and third means coupled between said source of data signals and each of said capacitors for charging each said first capacitor to a second level equal to or greater than cathode ionization potential when a data sIgnal is present at said third means, said first means including a separate lead connected from said data source to each said anode and through a resistive path to first and second semiconductor devices in series, a bus coupled through separate diodes to each of said capacitors, the output of said first and second semiconductor devices being connected to said bus and to a current flow path which includes a first diode, said capacitor, a second diode, a resistor and a source of bias potential whereby each of said capacitors is charged to a relatively low level and holdoff potential is applied to each of said common conductors and said cathode elements do not exhibit cathode glow, said third means including separate semiconductor devices connected between said data source and each of said capacitors, each of said separate semiconductor devices being in a conducting state when no data signals are applied to it from said data source whereby its associated capacitor is held at said low level, each said capacitor being charged to a relatively high level at which its associated cathode can exhibit cathode glow when said first and second semiconductor devices are not conducting, and its associated separate semiconductor device receives data signals from said data source and is not conducting.
 7. Multiple-position display device and system for operating the device, said device comprising a gas-filled envelope including a plurality of groups of cathode electrodes and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common cathode conductor for each cathode electrode in each of said groups, said system comprising a first bus connected to all of said common conductors, a semiconductor logic circuit including: a plurality of output leads, each coupled through a capacitor to one of said common cathode conductors for applying data signals thereto, an anode lead coupled to each of said anodes, a plurality of input leads, and means by which a clock signal can be applied to the logic circuit to sequence the logic circuit, and a keyboard having: a plurality of keys, each representing a unit of information; a plurality of output leads, one from each key and connected to one of said input leads to said logic circuit; and a plurality of strobe leads, each connected to one of said anode leads of said logic circuit and thus to one of said anodes, each of said anode leads and the keyboard strobe lead to which it is connected being coupled through a pulse-generating circuit to said bus which is connected to said common cathode conductors, whereby at a character position when the anode is energized and driven in a positive direction, all of said common cathode conductors and one side of said capacitor are driven in a negative direction, the presence of a cathode data signal on any one of said output leads from said logic circuit appearing at the other side of the associated one of said capacitors and driving the associated common cathode conductor sufficiently negative to cause the cathode associated with the energized anode to exhibit cathode glow, the absence of a cathode data signal on any one of said output leads from said logic circuit preventing any of said capacitors from charging to a potential sufficient to cause the associated cathode to exhibit cathode glow.
 8. The system defined in claim 7 and including a second bus, said pulse generating circuit including a first semiconductor device having input and output electrodes and a current flow path therethrough, and a second semiconductor device having input and output electrodes and a current flow path therethrough, all of said anodes being connected to said second bus, said second bus itself being coupled (1) through an anode pull-down resistor to a negative power supply, and (2) to the input of said first semiconductor device of said pulse-generating circuit, The output of said first semiconductor device of said pulse-generating circuit being coupled through another capacitor and a resistive path (1) to the input of said second semiconductor device, (2) to the current flow path through said second semiconductor device, and (3) to said first bus, said first bus thus being connected to said current flow path through said second semiconductor device and to all of said common cathode conductors.
 9. Multiple-position display device and system for operating the device, said device comprising a gas-filled envelope including a plurality of groups of cathode electrodes and an anode associated with each group, corresponding cathodes of the different groups being interconnected by a single common conductor, there thus being a single common cathode conductor for each cathode electrode in each of said groups, said system comprising a first bus connected through individual coupling capacitors to each said common conductor, a semiconductor logic circuit including: a plurality of output leads, each coupled through a separate pulse-generating semiconductor device and one of said coupling capacitors to one of said common cathode conductors for applying data signals thereto, an anode lead coupled to each of said anodes, a plurality of input leads, and means by which a clock signal can be applied to the logic circuit to sequence the logic circuit, a single common pulse-generating circuit, and a keyboard having: a plurality of keys, each representing a unit of information; a plurality of output leads, one from each key and connected to one of said input leads to said logic circuit; and a plurality of strobe leads, each connected to one of said anode leads of said logic circuit and thus to one of said anodes, each of said anode leads and the keyboard strobe lead to which it is connected being coupled through said common pulse-generating circuit to said bus and thus through each said coupling capacitor to one of said common cathode conductors, whereby at a character position when the anode is energized and driven in a positive direction, if the associated pulse-generating semiconductor device receives a data signal from said logic circuit, then the associated cathode exhibits cathode glow.
 10. The system defined in claim 9 and including a second bus, a third bus, a fourth bus, and a fifth bus, said second bus being coupled through an anode pull-down resistor to a negative power source and to the input of said pulse-generating circuit, the output of said pulse-generating circuit being coupled to said first bus, said first bus being coupled through a diode to the side of each of said capacitors remote from the associated common cathode conductor, each said separate pulse-generating semiconductor device being coupled to said side of its said capacitor through its output electrode, each of said data lines being coupled to the input of one of said pulse-generating semiconductor devices.
 11. The system defined in claim 10 wherein said pulse-generating circuit comprises first and second PNP transistors connected in series, and each said pulse-generating semiconductor device comprises a third PNP transistor.
 12. The system defined in claim 10 wherein said pulse-generating circuit comprises first and second PNP transistors connected in series, and each said pulse-generating semiconductor device comprises a third PNP transistor, said second bus being connected to the base of said first PNP transistor, said third bus being connected through a resistive path to the base of each of said third PNP transistors, said fourth bus being connected to the emitter of each of said third transistors, and said first bus being connected to the collector of said second PNP transistor. 